1. Field of the Invention
The invention relates to an expansion valve the gas outlet coupling of which comprises an external profile suited to taking a user connector with a complementary internal profile, preferably a expansion valve with a non-adjustable reduced pressure for gas cylinders, particularly those which may be used in the field of food, particularly for drinks, in the field of welding, in laboratories or the like.
2. Related Art
Existing gas valve assemblies with built-in pressure reducers, also known as expansion valves, like the one described in document EP-A-0747796, usually have at least one device for interrupting the delivery of high-pressure gas, a pressure reducer, a system for adjusting the pressure and the flowrate, and a coupling for the gas outlet and to which the user can connect.
The device for interrupting the delivery of high-pressure gas is composed mainly either of the valve shutter of the pressure reducer when the expansion valve assembly has just one shutter, or of a shutter separate from the pressure-reducing shutter, when the expansion valve assembly has several valve shutters, generally two shutters.
When the operator wishes to obtain gas, he has therefore to perform two or even three successive operations, namely to connect a gas outlet coupling to the body of the expansion valve assembly, to open the gas passage by operating a valve or a control lever on the gas outlet, and possibly to adjust the flowrate and/or the pressure of the gas to the desired value.
Now, in a certain number of uses or applications, these successive operations on the part of the user on the expansion valve assembly may give rise to:                a risk of error leading to malfunctioning, particularly on the part of users who have little or no technical awareness, which is, in particular, the case in the application to the tapping off of CO2, because the users of CO2 in packaged form are, in particular, proprietors or managers concerned with delivering drinks, such as beer or other sparkling beverages which are served on tap in this type of establishment, particularly fizzy drinks, and        a significant length of time spent using the gas, which may sometimes prove to take quite a long time until the desired result is obtained.        
In an attempt at solving this problem, an expansion valve which is simpler to use than the conventional expansion valves, even for users with no particular technical awareness as it has a reduced number of operations that need to be performed when the user taps off gas, has already been proposed and this valve being characterized by the presence of a gas outlet coupling which can take a user connector and which delivers reduced-pressure gas at a reduced pressure that the user cannot adjust, that is to say at a predetermined fixed pressure of, for example, 8 bar.
Now, at the present time, gas outlet couplings of this type of expansion valve are all practically identical or differ from one another only very slightly, which means that there may be a significant risk of error, when the user connection is being connected or coupled to the said coupling by an ill-informed operator.